Method for allocating resources to uplink control channel

ABSTRACT

A method for adaptively allocating resources of an uplink control channel according to a system situation is disclosed. If a base station (BS) recognizes the system situation, establishes control information for resource allocation, and transmits the control information to a mobile station (MS), the mobile station (MS) allocates resources for transmitting uplink control information using a specific block or a specific resource distribution method according to the corresponding control information. The system situation may be changed according to the number of users contained in the BS&#39;s coverage or the usage of a multi-antenna. The variation of the system situation is actively reflected so that the uplink channel resources can be effectively used.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/980,260, filed on Dec. 28, 2010, now U.S. Pat. No. 8,953,530, whichis a continuation of U.S. patent application Ser. No. 11/865,639, filedon Oct. 1, 2007, now U.S. Pat. No. 7,907,567, which claims the benefitof earlier filing date and right of priority to Korean PatentApplication No. 10-2007-0033297, filed on Apr. 4, 2007, and also claimsthe benefit of U.S. Provisional Application No. 60/827,640, filed onSep. 29, 2006, the contents of which are all hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method for adaptively allocatingresources of an uplink control channel according to the situation of asystem.

Discussion of the Related Art

The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)system includes one or more physical channels and a logical channelmapped to the one or more physical channels. The logical channels areclassified into a control channel, a common channel, a dedicated controlchannel, and a traffic channel, etc. Specifically, an example of theuplink control channel may be a Channel Quality Information CHannel(CQICH).

A conventional method for allocating resources to the uplink controlchannel is a pre-reserved method. The pre-reserved method estimates theamount of control information to be transmitted to an uplink,pre-reserves the proper amount of uplink resources, and allows aplurality of users to share the corresponding resources.

The pre-reserved method has an advantage in that there is no need totransmit downlink control information capable of transmitting a commandassociated with a resource allocation method to a mobile station (MS).However, it has difficulty in properly coping with some troublesomesituations caused by the insufficient or excessive amount ofpre-reserved resources.

In other words, the number of users contained in a coverage of a basestation (or Node-B) or the amount of various control information fedback to the uplink may be changed to others according to the situationof a system. The above-mentioned system situation may indicate thenumber of users of an uplink channel, specific information indicatingwhether the uplink control channel is used or not, the amount of data orcontrol information transferred via the uplink control channel, thedegree of interference, specific information indicating whether amulti-antenna is used, a channel quality information transmissionscheme, and a channel situation, etc.

In this case, if the number of users of the uplink channel increases, orthe amount of uplink-channel control information increased by the mobilestation (MS) based on a multi-antenna scheme is greater than the amountof pre-reserved resources, the pre-reserved method must transmit theuplink-channel control information several times, so that it is unableto implement smooth communication between a transmission end and areception end. Otherwise, if the small number of users is located in thebase station's coverage and the amount of control information to betransferred to the uplink is low, the pre-reserved method has adisadvantage in that it unconditionally allocates all of pre-reservedresources including unnecessary resources not to be used to the users,resulting in the occurrence of wasted resources.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method forallocating resources to an uplink control channel that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a method for adaptivelyallocating resources to an uplink control channel according to thenumber of users contained in the base station's coverage and thevariation of an amount of feedback information.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, aresource allocation method for transmitting uplink control informationin a mobile communication system comprising: receiving, by a mobilestation (MS), control information established by a base station (BS) inconsideration of a system situation; and allocating resources of anuplink control channel according to the received control information.

In another aspect of the present invention, there is provided a methodfor transmitting downlink control information to allocate resources ofan uplink channel in a mobile communication system comprising:generating, by a base station (BS), control information for allocatingresources of an uplink control channel in consideration of a systemsituation; transmitting the control information to a mobile station(MS); and allocating resources of the uplink control channel accordingto the control information.

Preferably, the system situation includes at least one of the number ofuplink/downlink users, an amount of transmission data, an amount ofcontrol information, a channel situation, a channel quality informationtransmission scheme, an amount of allocation resources, an amount ofavailable resources, an interference degree, and an allocation locationof a control channel.

Preferably, the control information for allocating resources of theuplink control channel includes at least one of an amount of allocationresources required for smoothly transmitting the uplink controlinformation and the appropriate resource allocation location.

Preferably, the resource allocation location includes at least one ofinformation indicating a resource area where the uplink controlinformation is to be transmitted, and information indicating a resourcedistribution scheme.

In this case, the resource distribution scheme can be classified into apartial transmission method and a repetitive transmission method. If anarea for transmitting the control information is larger than a maximumarea/capacity capable of being allocated to a single symbol or a singlesub-frame, the partial transmission method divisionally transmits thecorresponding control information over several symbols or sub-frames.The repetitive transmission method may be used along with the partialtransmission method or may be used separately from the partialtransmission method, so that it controls the uplink control informationto be repeatedly transmitted over several sub-frames.

The extended block of the partial transmission method may belong to asymbol to which the basic block belongs, a symbol equal to a sub-frame,or a sub-frame. And, the extended block may belong to a symbol to whichthe basic symbol belongs, a symbol different from a sub-frame, or asub-frame.

The resource allocation for the extension or repetition of the partialor repetitive transmission method is implemented by a frequency-hoppingaction for each sub-frame.

Preferably, the resources may be allocated to maintain a single-carriercharacteristic between constituent information units of the uplinkcontrol information.

Preferably, the resources may be allocated to maintain a single-carriercharacteristic between the uplink control information and the uplinkdata.

The uplink control information may be CDM- or TDM-multiplexed along withthe uplink user data, so that the multiplexed uplink control informationmay be transmitted to a destination.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a conceptual diagram illustrating a method for allocatingresources to an uplink control channel according to the presentinvention;

FIG. 2 is a conceptual diagram illustrating an example of a resourcedistribution method from among the inventive resource allocation methodsaccording to the present invention;

FIG. 3 is a conceptual diagram illustrating a method for multiplexinguplink control information from among the inventive resource allocationmethods according to an embodiment of the present invention; and

FIG. 4 is a conceptual diagram illustrating a method for multiplexinguplink control information from among the inventive resource allocationmethods according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

The following techniques to be disclosed will be used for a variety ofcommunication systems. The communication systems are deployed to a widerange of areas to provide users with a variety of communication services(e.g., voice or packet data). The above-mentioned techniques may beapplied to a downlink or uplink. In this case, the downlink indicatesdata communication from a base station (BS) to a mobile station (MS),and the uplink indicates data communication from the mobile station (MS)to the base station (BS).

Generally, the base station (BS) indicates a fixed station communicatingwith the mobile station (MS), and may also be called a Node-B, a BTS(Base Transceiver System), or an Access Point (AP), etc. The mobilestation (MS) may be fixed at a specific location or may have themobility, so that it may also be called a user equipment (UE), a userterminal (UT), a subscriber station (SS), or a wireless device, etc.

FIG. 1 is a conceptual diagram illustrating a method for allocatingresources to an uplink control channel according to the presentinvention.

<Operations of Base Station (BS)>

The base station (BS) establishes control information required forallocating resources to an uplink control channel in consideration of asystem situation, and transmits the established control information tothe mobile station (MS).

In FIG. 1, the A area indicates a resource allocation area of a downlinkcapable of transmitting the above-mentioned control information to themobile station (MS).

The system situation which must be recognized by the base station (BS)includes at least one of a variety of information, for example, thenumber of uplink/downlink users, the amount of downlink transmissiondata, an amount of uplink control information, a channel situation, amethod for transmitting the channel quality information, an amount ofcurrently-allocated resources, an amount of current available resources,the degree of interference between users, and an allocation location ofa control channel.

The control information transmitted to the downlink by the base station(BS) to implement the scheduling includes at least one of an amount ofallocation resources required for smoothly transmitting uplink controlinformation and an allocation location.

In this case, the allocation location contained in the above-mentionedcontrol information includes at least one of a block (LB or SB) capableof transmitting the control information and a resource-localized method(also called a resource-distributed method). The block LB or SB to betransmitted and the resource-localized method will hereinafter bedescribed in detail.

<Operations of Mobile Station (MS)>

The mobile station (MS) refers to not only the amount of uplink controlinformation contained in the above-mentioned control information butalso the resource allocation location contained in the same, andtransmits resources of the uplink control channel.

In FIG. 1, the B area indicates a resource allocation area of a downlinkcapable of transmitting the above-mentioned control information to themobile station (MS). In other words, the B area is indicative of aspecific area scheduled by control information received from the basestation (BS). The B area is variable with the amount of controlinformation, and the location and size of the B area is dynamically orsemi-statically established.

<Uplink Control Information>

The uplink control information is classified into first controlinformation, second control information, and third control information.

The first control information is directly related with transmission ofuplink data, and a representative example is a TFCI. The second controlinformation is not directly related with the transmission of uplinkdata, and a representative example is a CQI or ACK/NACK. The thirdcontrol information allows the base station (BS) to measure a channel ofdata transmitted to the uplink, and a representative example is a CQpilot.

The present invention can be equally applied to not only the first tothird control information but also a variety of control informationtransferred to the uplink.

FIG. 2 is a conceptual diagram illustrating an example of a resourcedistribution method from among the inventive resource allocation methodsaccording to the present invention.

The downlink control information for scheduling uplink resources mayinclude information associated with the method for allocating the uplinkresources. Specifically, if control information is variable, thedownlink control information may also include information indicating aresource transmission method capable of accommodating the variablecontrol information.

<Block Desired to Transmit Uplink Control Information>

According to the LTE assumption, a single sub-frame of the uplinkincludes 6 long blocks (LBs) and 2 short blocks (SBs). The number of LBsor SBs may be changed to another at a later time, so that it is assumedthat a symbol used for transmitting the uplink control information isbasically denoted by “LB”, however, the symbol may also be denoted by“SB” as necessary.

Generally, the SB is established on the assumption that a referencesignal is transmitted, so that it is difficult for high-capacity controlinformation (e.g., CQI) to be added to the SB. In other words, the SB isnot enough to additionally involve the high-capacity controlinformation.

Therefore, the uplink control information according to the presentinvention is basically transferred via the LB, however, it should benoted that low-capacity uplink control information (e.g., ACK/NACK) canbe transferred to via not only the LB but also the SB.

<Resource Distribution Method>

The resource distribution method can be classified into a partialtransmission method and a repetitive transmission method.

If an amount of uplink control information is larger than apredetermined level, the partial transmission method divides the uplinkcontrol information into several information units, and transmits thedivided information units, so that overall uplink control information isdivisionally transmitted to a destination.

The repetitive transmission method transmits control information N timesover several symbols or several sub-frames, so that it increases areception reliability of the control information. For example, if thevalue of N is 2, the repetitive transmission method may transmit thecontrol information twice.

The partial transmission method is adapted to transmit uplink controlinformation (e.g., CQI) of a relatively high capacity.

The repetitive transmission method is used for a specific case in whichthe same control information (e.g., ACK/NACK) must be repeatedlytransmitted according to the system situation.

However, the same resource distribution method is applied to the partialtransmission method and the repetitive transmission method, so that thefollowing detailed description of the partial transmission method willsubstitute for that of the repetitive transmission method.

<Partial Transmission Method>

The relatively high-capacity uplink control information such as CQI maynot be simultaneously transmitted to a single resource area unit. Inthis case, the mobile station (MS) transmits the corresponding uplinkcontrol information over a plurality of resource areas.

In this case, if the control information is variable so that it islarger than a basic unit for transmitting the control information, thepartial transmission method can transmit the control information overseveral symbols or several sub-frames. In this case, it is basicallyassumed that the control information between users is multiplexedaccording to a CDM (Code Division Multiplexing) or TDM (Time DivisionMultiplexing) scheme so that the multiplexed control information istransmitted to the users.

Specifically, the partial transmission method may extend the partexceeding the single basic transmission unit to the next basictransmission unit, and may also extend the above-mentioned part toresource areas spaced apart from each other. In this case, the resourcearea indicates an area composed of a frequency area and a time area, andthe basic size of the resource area may be established in different waysaccording to the system situation.

The amount of uplink control information to be fed back to the basestation (BS) may increase or decrease due to the variation of the systemsituation. A representative exemplary case in which the uplink controlinformation increases may be a specific case in which a currentsingle-antenna system is changed to a multi-antenna system such as aMIMO system.

For example, in the case of comparing a first case employing the MIMOsystem with a second case unemploying the MIMO system, the amount offeedback control information of the first case may be much larger thanthat of the second case. In more detail, the first case employing theMIMO system requires B resource-units whereas the second caseunemploying the MIMO system requires A resource-units (where, AB). Inthis case, the area for transmitting the control information is extendedso that the control information may be transmitted over several symbolsor several sub-frames.

For example, provided that the control information transferred to theuplink is the CQI, the system uses a DCT (Discrete CosineTransform)-based CQI transmission scheme, and the CQI to be transmittedexceeds a single resource area, the CQI is distributed to severalresource areas (i.e., several symbols or several sub-frames) and is thentransmitted over the several symbols or sub-frames.

For example, if the CQI is multiplexed according to the TDM scheme andthe magnitude of the DCT-processed CQI is M, M/2 is assigned to a firstsub-frame, and the other M/2 is assigned to a second sub-frame.Preferably, if the CQI accuracy is more important than the systemcomplexity, the CQI may be newly DCT-processed for each sub-frame, andsome parts of the DCT-processed CQI may be transmitted to a desireddestination.

If the CQI is multiplexed according to the TDM scheme while the Best-MCQI transmission method is used, M/2 information from among the Minformation is assigned to a first sub-frame and the other M/2information is assigned to a second sub-frame, so that the CQI isdivisionally transmitted. If the partial transmission method and therepetitive transmission method are simultaneously used, each informationis repeated so that the repeated information is transmitted over foursub-frames. If the CDM scheme is used, the CQI may be multiplexedsimultaneously while maintaining orthogonality over allocated resourceareas, or be CDM-processed for each basic transmission unit, so that theresultant CQI is transmitted to a desired destination.

In the meantime, although the same MIMO modes are provided, the amountof CQI to be fed back may be changed to another amount according tocategories of a codeword to be transmitted. In this case, the method fortransmitting control information over the extended resource areas mayalso be applied to the above-mentioned case in which the amount offeedback CQI is changed to another amount according to the codewordcategories.

For example, if data is TDM-multiplexed by a system equipped with a TTIcomposed of two sub-frames, the system transmits the CQI using only thefirst sub-frame during the non-MIMO mode. Thereafter, if the non-MIMOmode is changed to the MIMO mode, the system distributes the CQI to twosub-frames so that it transmits the CQI over the two sub-frames.Needless to say, if the CQI includes four streams, two streams may beassigned to each sub-frame, so that the four streams can be transmittedvia the two sub-frames.

According to the code division multiplexing (CDM) scheme, the CQI isCDM-processed over the extended resource areas (e.g., two sub-frames),or is CDM-processed for each basic transmission unit, so that theresultant CQI is transmitted to a desired destination.

The above-mentioned partial transmission method may be extended to atleast two sub-frames.

In other words, if the amount of feedback information to be transmittedis M, M−P1 (where P1 M) is transmitted to the first sub-frame, M−P1−P2(where P2 M) is transmitted to the second sub-frame, and M−P1−P2 . . .−PK (PK<M, P1+P2+P3+ . . . +PK=M) is fed back to a K-th frame.

In the case of the CDM scheme, data is CDM-processed over all extendedareas or is CDM-processed for each basic transmission unit, so that theresultant data is transmitted to a desired destination.

<Index Transmission Scheme>

As described above, the present invention determines whether the mobilestation (MS) uses the non-MIMO mode or the MIMO mode, decides torepeatedly transmit target information or decides to divisionallytransmit the target information over the extended areas according to thedetermined mode, so that it must inform the mobile station (MS) of theabove-mentioned decision result. Therefore, the number of various casescapable of commanding the above-mentioned decisions may occur, so thatthe amount of control information of a downlink channel unavoidablyincreases.

Therefore, the present invention indicates whether the mobile station(MS) is in the MIMO mode or the non-MIMO mode using only one bit,indicates whether the control information is repeatedly transmittedusing only one bit, and indicates whether the control information isdivisionally transmitted using only one bit, so that it can representall the number of cases using index information composed of 3 bits.

The present invention includes a table associated with theabove-mentioned index information in each of the base station (BS) andthe mobile station (MS), so that the amount of downlink-channel controlinformation can be reduced.

An exemplary index table for notifying the ACK/NACK partial transmissionand the CQI partial transmission on the condition that the MIMO mode ispre-notified is shown in the following Table 1:

TABLE 1 ACK/NACK CQI repetitive partial Index MIMO transmissiontransmission 0 X X X 1 X ◯ ◯ 2 ◯ X ◯ 3 ◯ ◯ ◯

Provided that the MIMO mode of the mobile station (MS) can bepre-recognized, the above-mentioned index table indicates whether theACK/NACK is repeatedly transmitted on the condition that only theACK/NACK has been designed to be repeatedly transmitted, or indicateswhether the CQI is partially transmitted on the condition that only theCQI has been designed to be transmitted over the extended areas.

<Frequency Hopping>

According to the above-mentioned partial transmission method, partstransmitted over the extended area need not always to be located at thesame sub-frame or the same locations within different sub-frames. Also,the repeated parts for use in the repetitive transmission method neednot to be located at the same location within the sub-frames.

FIG. 3 is a conceptual diagram illustrating the repetitive transmissionmethod from among the inventive resource allocation methods.

As can be seen from FIG. 3, the uplink control information (e.g.,ACK/NACK or CQI) is transmitted from the frequency-A area, and hops ontothe frequency-B area during the repetitive transmission case, so that itis transmitted over the A and B areas. In this case, the basic hoppingperiod (i.e., symbol, sub-frame, and other prescribed length) may beestablished in various ways.

<Partial Pre-Reserved Method>

If the base station (BS) separately decides the block information (SB orLB) for allocating uplink resources via downlink control information, arepetitive- or partial transmission-method, and a localized/distributedmethod, the base station (BS) can effectively use uplink resources dueto the smoothly-allocated resources, however, the amount of downlinkcontrol information increases. Therefore, there is needed an improvedmethod capable of providing the flexibility of a predetermined level tothe above-mentioned method for allocating uplink resources,simultaneously while reducing the amount of downlink controlinformation.

Therefore, different resource distribution methods according to thecategory of a block for uplink resource allocation and the category ofuplink control information are pre-engaged between the base station (BS)and the mobile station (MS). The base station (BS) allocates resourcesto the above-mentioned block according to the above-mentioned resourcedistribution method, so that a trade-off between a first requirement forguaranteeing the resource allocation flexibility and a secondrequirement for minimizing the amount of downlink control informationcan be made available.

<Maintenance of Single-Carrier Characteristic>

In order to maintain single-carrier characteristic between uplinkcontrol information pieces, a CQ pilot is periodically transmitted tothe uplink while being allocated to a single symbol or all symbols (or asingle block or all blocks), and is then transmitted to a desireddestination. Preferably, the ACK/NACK and the CQI may not besimultaneously transmitted to different frequency bands.

As can be seen from FIG. 3, a sub-frame in the transmission case of theCQ pilot is different from that in the non-transmission case of the CQpilot.

Therefore, provided that the sub-frame including the CQ pilot is calledan A type, and the other sub-frame including no CQI pilot is called a Btype, the A and B types can be transmitted to a variety of combinationsaccording to transmission periods of the CQ pilot. For example, the CQpilot can be transmitted in the order of A→B→B→A→B→B. In other words,the CQ pilot may be periodically transmitted or may also benon-periodically transmitted.

Preferably, the single-carrier characteristic between the uplink controlinformation and uplink user data may be maintained. For example, thereis no problem in a specific case in which only control information istransmitted without involving uplink data. However, if a user mustsimultaneously transmit the data and the control information, he or shemay perform a single DFT on the transmission data or information tomaintain the single-frequency characteristic, and may transmit theDFT-processed result along with the transmission data or information.

The present invention can adaptively allocate uplink resources to atarget object according to the number of users contained in the basestation's coverage and the variation of an amount of feedbackinformation, so that it can effectively use the resources, resulting inan increased communication throughput between a mobile station (MS) anda base station.

It should be noted that most terminology disclosed in the presentinvention is defined in consideration of functions of the presentinvention, and can be differently determined according to intention ofthose skilled in the art or usual practices. Therefore, it is preferablethat the above-mentioned terminology be understood on the basis of allcontents disclosed in the present invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A method for transmitting uplink controlinformation at a mobile station (MS) in a mobile communication system,the method comprising: mapping reference signals (RSs) at two or moretime domain units, separated from each other in time domain, within onetransmission time interval (TTI) of a 2-dimensional time-frequencyresource grid; multiplexing the uplink control information with uplinkdata based on one or more of time divisional multiplexing (TDM) orfrequency divisional multiplexing (FDM) by mapping the uplink controlinformation and the uplink data to the 2-dimensional time-frequencyresource grid, wherein the uplink control information comprises one ormore of an ACK/NACK and a CQI, and wherein the one or more of theACK/NACK and the CQI are mapped at each of time domain unitsrespectively adherent to each of the two or more time domain units inwhich the RSs are mapped within the one TTI; and transmitting the RSs,the uplink control information and the uplink data mapped to the2-dimensional time-frequency resource grid to a base station.
 2. Themethod of claim 1, wherein the RSs comprises a first type RS for datademodulation.
 3. The method of claim 1, wherein the RSs comprises asecond type RS is for channel quality measurement, and wherein thesecond type RS is periodically transmitted.
 4. The method of claim 3,further comprising: puncturing one time domain unit, among the timedomain units where the uplink control information is mapped, if thesecond type RS and the uplink control information are to besimultaneously transmitted within a specific TTI.
 5. A mobile station(MS) for transmitting uplink control information in a mobilecommunication system, the MS comprising: a processor configured to: mapreference signals (RSs) at two or more time domain units, separated fromeach other in time domain, within one transmission time interval (TTI)of a 2-dimensional time-frequency resource grid, and multiplex theuplink control information with uplink data based on one or more of timedivisional multiplexing (TDM) or frequency divisional multiplexing (FDM)by mapping the uplink control information and the uplink data to the2-dimensional time-frequency resource grid, wherein the uplink controlinformation comprises one or more of an ACK/NACK and a CQI, and whereinthe one or more of the ACK/NACK and the CQI are mapped at each of timedomain units respectively adherent to each of the two or more timedomain units in which the RSs are mapped within the one TTI; and atransmitter configured to transmit the RSs, the uplink controlinformation and the uplink data mapped to the 2-dimensionaltime-frequency resource grid to a base station.
 6. The MS of claim 5,wherein the RSs comprises a first type RS for data demodulation.
 7. TheMS of claim 5, wherein the RSs comprises a second type RS is for channelquality measurement, and wherein the second type RS is periodicallytransmitted.
 8. The MS of claim 7, wherein the processor furtherconfigured to puncture one time domain unit, among the time domain unitswhere the uplink control information is mapped, if the second type RSand the uplink control information are to be simultaneously transmittedwithin a specific TTI.